An integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on a small piece of semiconductor material, normally silicon. ICs are used in virtually all electronic equipment today and have revolutionized the world of electronics. Computers, mobile phones, and other digital home appliances have been made possible by the low cost of ICs and are now inextricable parts of the structure of modern societies. ICs can be made very compact, for example, having up to several billion transistors and other electronic components in an area the size of a fingernail.
Due to the complexities involved in manufacturing ICs, it is important to test these ICs for functional defects prior to distributing them to customers. Testing can be performed by a piece of test equipment called a probe station, which presses tiny probes onto pads on the individual ICs. Once these probes are pressed onto the IC pads, input test vectors (e.g., a series of “1”s and “0”s for a digital IC) are applied to the IC. Based on these input test vectors, the circuitry on the IC outputs digital output values (i.e., test results). If the measured test results are the same as predetermined expected test results, which were set based on the underlying IC design as envisioned by designers, then the chip is deemed to meet design specifications. On the other hand, if the measured test results do not correspond to the expected test results, then the chip is a failure. Chips can be “binned” in some cases where failures are not necessarily fatal or in other cases where chips perform at higher performance levels than design specifications.